This invention relates generally to dental appliances and more particularly to an appliance for the diagnosis and treatment of temporomandibular joint dysfunction.
The temporomandibular joints are located on opposite sides of the cranium. On each side, the mandible has a smoothly curved condyle which is received in a matching fossa in the cranium. A meniscus or articular disc is located between the condyle and fossa to provide a cushion between them. Numerous masticatory muscles connect to the mandible to provide for any combination of horizontal and vertical movements relative to the maxilla. It is well known that temporomandibular joint dysfunction is normally caused by malocclusion due to misalignment of the mandible with the maxilla and/or some of the upper and lower teeth. Proprioceptive nerve endings in the periodontal ligaments surrounding the roots of the teeth send messages that control the manner in which the masticatory muscles close the mandible. The primary function of this myo-neural mechanism is to protect the teeth, supporting bone, and soft tissue from the adverse affects of malocclusion. The muscles, while functioning in disharmony, react and bruxism or grinding is initiated in an effort to correct the malocclusion. The result is mild to severe muscle fatigue and in some cases a complete derangement of the temporomandibular joint whereby the articular discs are pulled forward leaving the condyles to function on the retro-discal fibres and the cranial fossae. While temporomandibular joint dysfunction has various symptoms such as neck and ear pain, it usually causes acute and/or chronic headaches which are frequently mistakenly attributed to other causes such as stress or migraine.
Previous attempts to overcome this problem fall into two categories. The first category is appliances which are worn by a person to relieve pain or to reposition the mandible. The second category is devices which are temporarily placed in the mouth of a patient during a dental procedure. An example of the first category is shown in Canadian patent number 1,136,450 to Lerman which issued Nov. 30, 1982 wherein a fluid containing portion of the appliance extends between the upper and lower teeth. Other examples of this category are seen in Canadian patent numbers 1,147,583 to Dufour which issued Jun. 7, 1983, 1,221,254 to Ahlin which issued May 5, 1987 and U.S. Pat. No. 4,671,766 to Norton which issued Jun. 9, 1987 all of which show various appliances to be worn to relocate the mandible to its proper position. Examples of devices in the second category which are used during balancing of dentures or teeth are shown in U.S. Pat. No. 3,068,570 to Thompson et al which issued Dec. 18, 1962 and U.S. Pat. No. 4,964,769 to Hass which issued Oct. 23, 1990. The devices in the second category have the disadvantage that they are not suitable for wear over any extended period of time, while the appliances in the first category have the disadvantages that they are not comfortable to wear and do not satisfactorily relieve the symptoms of temporomandibular joint dysfunction.